Final answer:
The sentence in question uses the past tense, indicated by the verbs 'went' and 'bought'. The present tense forms would be 'go' and 'buy', showing a completed action in the past.
Step-by-step explanation:
The sentence 'When we went to the store, we bought five bags of groceries.' is written in the past tense. The action of going to the store and buying groceries happened in the past. We can determine the tense of the sentence by looking at the verbs used. In this case, 'went' and 'bought' are both in the past tense.
This contrasts with the present tense, where the verbs would be 'go' and 'buy'. We can see the usage of the past tense form in verbs through several examples, such as begin/began/begun, bring/brought/brought, buy/bought/bought, and so on. It is important to maintain tense consistency throughout writing to provide clarity and a coherent timeline of events.